Joints and Articulations

Joints and Articulations By Scott Ford, M.Ed.

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Histology of Cartilage

Histology of Cartilage • Cartilage is created by chondroblasts • Remember the bone is made by osteoblasts • chondro = cartilage • osteo = bone • Blasts make stuff • The chondroblast will secrete a matrix that will surround it, eventually trapping it in a lacunae (sounds like cocoon) • When it is encased in its lacunae it is known as a chondrocytes • Remember that an adult bone cell is known as an osteocyte

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Joints and Articulations

Histology of Cartilage • The main function of cartilage is to support soft tissues • Cartilage has a smooth surface, and is able to withstand a good deal of stress and acts as a shock absorber • Perfect as a cushion between bones • Strength of the cartilage is due to the collagen fibers • Can act as a placeholder for developing bones • When a baby is born not all his/her bones are done growing. The cartilage fills in till the bone can take its place • Can form supporting framework for some organs, like the nose, trachea, and larynx

Histology of Cartilage (continued) • Cartilage lacks a direct blood supply, as such it must get its nutrition and waste removal from diffusion • This is why cartilage take so long to heal • There are three types of cartilages, classified by the type and amount of fibers contained • Hyaline • Fibrocartilage • Elastic

Hyaline • aka “Gristle” • Most abundant cartilage in body • Has a glassy appearances • Hyalo (Greek for glass) • Function: • Gives us flexibility and support • At joints acts like shock absorber • In the embryo it serves as a temporary skeleton till the bones form • Found: • Articular surface of movable joints • Walls of larger respiratory passages- nose, larynx, trachea • Ventral end of ribs were the articulate with the sternum

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Joints and Articulations

Epiphyseal Plate • aka “Growth Plate” • Found between diaphysis and epiphysis of growing lone bone • Plate is responsible for longitudinal growth in the bones • Ossification of all bones is usually completed by age 25

Fibrocartilage • Has strength and rigidity • The strongest of the three cartilages • Found in areas of the body were there is a great deal of stress • Such as weight bearing • Found: • Intervertebral disks • Symphysis pubis • Meniscus

Elastic • The most pliable and stretchable of the three types of cartilage • Provides strength and elasticity and maintains shape of certain organs • Found: • Auricle of the ear • Visible portion of the external ear • Walls of external auditory canals • Eustachian tubes • Epiglottis Scott Ford © 2013 All Rights Res erved

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Joints and Articulations

Some Quick Vocabulary • Arthrology • The study of joints • Kinesiology • The study of human movements, musculoskeletal movement • http://www.americankinesiology.org/ • Mocap • Motion capture, the process of recording the movements of people or objects for use in simulations, movies, and games

Joint Fundamentals • Movable joints provide mechanism that allows the body to move • Two ways to classify joints (they are not mutually exclusive) • Function (degree of movement) • Structure • Some classification will also just use a four category system: bony, fibrous, cartilaginous, and synovial • If you know one of these systems you are good either way

Joint Classification Joint Clas s ification

Degree of Movement

Synarthros is (none)

Amphiarthros is (s ome)

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Structure

Diarthros is (free)

Fibrous

Cartilaginous

Synovial

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Joints and Articulations

Classification Based on Functions Helpful mnemonic

• Degree of movement

SADISM • Synarthrosis • Immovable

Synarthrosis

• Amphiarthrosis • Slightly movable

Amphiarthrosis Slightly Movable

• Diarthrosis • Movable

Diarthrosis

Immovable

Movable

Classification Based on Structure • Type of classification system divides joints according to how the bones are connected to each other • Three structural classifications: • Fibrous • Cartilaginous • Synovial

Fibrous

Structure

Cartilaginous

Synovial

Classification Based on Structure • Three structural classifications: • Fibrous • Usually synarthrosis • Joined by fibrous connective tissue • Cartilaginous • Usually amphiarthrosis • Joined by cartilage • Synovial • Usually diarthrosis • Interestingly no direct connections (joint capsules are covered later)

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Joints and Articulations

Structural Classification: A Close Look • The structural classification uses three main categories: • These categories can be further subdivided

Structural Classification: A Close Look Fibrous • Suture • Syndesmosis • Gomphosis

Cartilaginous • Synchondrosis • Symphysis

Synovial • Hinge • Pivot • Condyloid • Gliding • Saddle • Ball-&-Socket

Fibrous Joints • Fibrous connective tissue (dense connective tissue) unites the bones together • Mostly immovable, although some have slight movement • Synarthrosis • No joint cavity • Three types • Suture • Syndesmosis • Gomphosis

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Joints and Articulations

Three Types of Fibrous Joints • Suture • Little to no movement • Found in skull • Fibrous tissue between the articulating bones • Syndesmosis • More movable • Articulating bones held together, but not touching by fibrous ligament • Slight movement •

Ex : ti b i o fi b u l a r j o i n t a n d a l s o s h a fts o f ra d iu s a n d u l na

• Gomphosis • Little to no movement • Peg in a socket • The tooth held in place by a periodontal ligament •

FYI: Th e re i s s o me s l i g h t mo v e me n t a t th i s j o i n t to a l l o w u s to fe e l h o w h a rd we a re b i ti n g i n to s o me th i n g a s we l l a s to fe e l wh e n s o me th i n g i s s tu c k b e twe e n o u r te e th

Cartilaginous Joints • The bones are united by a plate of hyaline cartilage or fibrocartilaginous disk • Most slightly movable, although some are immovable • Amphiarthrosis • Two types • Synchondrosis • Symphysis

Two types of Cartilaginous Joints • Synchondrosis • Temporary joint • Made of hyaline cartilage • Allows a long bone to grow • Makes up the epiphyseal plate • Symphysis • Bony surface bridged by a plate of fibrocartilage • Slight movement • Ex: symphysis pubis and also intervertebral joint (IVD)

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Joints and Articulations

Synovial Joint

Synovial Joint • Articulating bones move freely • Diarthrosis • Most complex of all joint types • Components to know: • Articular cartilage • Joint capsule • Joint cavity • Synovial fluid

Synovial Joint: Articular Cartilage • The end of each bone (epiphyses) is covered with a layer of hyaline cartilage • Around 2-3 mm thick • Functions: • Creates a smooth surface that helps reduce friction • Acts like a shock absorber

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Joints and Articulations

Synovial Joint: Joint Capsule • The capsule enclosed the cavity in connective tissues • Made of two layers • Outer Layer/Fibrous Capsule • Made of strong dense connective tissue • Helps joint withstands forces that would pull the bones apart • Inserted into the periosteum of the bone at the end of the bone • Wraps around the end of the bone • Completely encloses the outer part of the joint • Inner Layer/Synovial Membrane • Lines all structures inside the cavity except the bone where covered by the articular cartilage • Secretes the synovial fluid and contains macrophages that help remove debris from the joint

Synovial Joint: Joint Cavity • Also known as Articular Cavity • The two bones are separated by a small gap, this cap is knows as the joint cavity • It is filled with a substance known as synovial fluid

Synovial Joint: Synovial Fluid • A very slick fluid that is found within joint cavity • Lubricates and greatly reduces friction between bones • Similar in feel to raw egg whites • Synovial is partially derives from ovum, egg • Nourishes the articular cartilage and removes waste

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Joints and Articulations

Synovial Joint: Accessory Structures • There are some accessory structures that are important to function of some joints • Bursae • A small sac filled with synovial fluid • Found between bones and tendons and/or muscles around a joint • Its job is to reduce friction or act as a cushion between the structures • Ligaments • Tough fibrous connective tissue that attaches bone to bone • Important in stabilizing a joint • Tendons • Similar in composition to a ligament, fibrous connective tissue • Attaches muscle to bone, or muscle to other structures like the eyeball

Types of Synovial Joints

Types of Synovial Joints • Synovial joints have widest range of motions out of all other types of joints • There are 6 types of synovial joints: • Hinge • Pivot • Condyloid • Plane/Gliding • Saddle • Ball-&-Socket (C C ) 2 0 0 5 P ro d u n i s

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Joints and Articulations

Hinge • Curved (convex) end of one bone fits into curved (concave) end of another • Think door hinge • Good for flexion and extension • Ex: elbow*

(C C ) 2 0 0 5 P ro d u n i s

Pivot • A central bone pivot is surrounded by a collar bone and ligament • Make an OK sign with your right hand, and put a pencil through the O, that's a pivot • Good for supination, pronation, rotation • Ex: Proximal radioulnar joint, C1-C2 (atlantoaxial joint) joint

(C C ) 2 0 0 5 P ro d u n i s

Condyloid • Modified ball and socket • One articulation is concave, the other convex • Good for flexion, extension, abduction, adduction, circumduction • Ex: Knuckles, (except the thumb )

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(C C ) 2 0 0 5 P ro d u n i s

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Joints and Articulations

Gliding • A flat surface on another flat surface, with the cartilage in-between • Simple gliding movements • Ex: between vertebrae

Saddle • The two bones have a convex and concave surface and they fit into each other • Good for abduction, adduction, opposition, reposition • Ex: thumb joint, when you ride in a western SADDLE you wrap your thumb around it • Almost always a test question

(C C ) 2 0 0 5 P ro d u n i s

Ball & Socket • The head of one bone fits into the concave process of another bone • Good for pretty much all the movements • Ex: shoulder joint, hip joint

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(C C ) 2 0 0 5 P ro d u n i s

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Joints and Articulations

Stability vs. Flexibility • There is an inverse relationship between stability and flexibility • As stability increases (the joint become more stable, less likely to dislocate) flexibility goes down Stability • As flexibility goes up the more likely joint is to be dislocated • Example: • The hip is less flexible then shoulder joint. Which one is more likely to be dislocated?

Flexibility

Movements at the Synovial Joints

General Movements Name of Movement

Description

Flexion

Bending motion, the angle between two bones decreases

Extension

Straightening motion, the angle between two bones is increased

Hyperextension

Extension beyond anatomical position

Abduction

Moving a limb away from the midline of the body.

Adduction

Moving the limb of the body closer to the body/midline. You "add" to the body

Rotation

The bone spins along its longitudinal axis

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Joints and Articulations

General Movements Name of Movement

Description

Medial Rotation Turning back to midline Lateral Rotation Moving away from midline Protraction

Forward movement, stick your jaw out

Retraction

Backward movement, bring your jaw back

Depression

Lowering a body part, lower your jaw, shoulders

Elevation

Raising a body part, raise your jaw, shoulders

General Movements Name of Movement

Description

Supination

Rotating hands so the palms are face up. Like making a bowl for soup

Pronation

The exact opposite of supination. Palms face down

Circumduction

One end of an appendage remains relatively still with the other end makes circular motions

Movements of the Hand Palmar Flexion Flexion of hand at wrist. Bring back of hand down Opposition

Move the thumb to touch any of the four fingers

Reposition

Return the thumb to its neutral position

Movements of the Feet Dorsiflexion

Flexion of the foot at ankle Bringing the top of your foot up

Plantar Flexion

Extension of foot at ankle joint, you are "planting" your toes

Inversion

Soles of feet come inward (INversion). You stand on the outsides of your feet

Eversion

Moving the soles of the feet outward.

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Joints and Articulations

Special Joints

Shoulder Joint • The shoulder joints consists of two joints • The primary joint is the Glenohumeral Joint • Articulation between the glenoid fossa of the scapula and the head of the humerus • The other joint found with the shoulder area is the Acromioclavicular • Between the acromion and the clavicle

Shoulder Joint: Glenohumeral Joint • Joint capsule encircles anatomical neck of humerus (proximal portion) and circumference of the glenoid cavity

• The Glenohumeral joint is a synovial joint and the most mobile joint in the human body: • Flexion

• There are several muscles (notably the Rotator Cuff muscles, discussed in the muscle lessons) and ligaments that help to reinforce the joint capsule, thus keeping the humerus in place

• Extension • Abduction • Adductions • Medial & Lateral Rotation • Circumduction

• There are several bursas associated with this joint

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Joints and Articulations

The Knee “Get plenty of calcium. Be kind to your knees, you’ll miss them when they’re gone.”

-Baz Luhrmann from Everybody's Free (To W ear Suns creen)

• The knee joint is the largest and most complicated of the synovial joints in human body. • A modified hinge joint: flexion, extension, with a wiggle side to side

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Joints and Articulations

The Knee: Ligaments • There are several important (must know) ligaments associated with knee: • Patellar ligament: • Many of the large muscles of the thigh form a common band of connective tissue the envelops and continues on to the tibia • Collateral ligaments • Tibial:from the medial condyle of the femur à medial condyle of tibia • Fibular:lateral condyle of the femur à head of the fibula

Anterior/Posterior Cruciate ligaments • Stretch from the tibia and femur • The name of each come from their attachments to tibia • Anterior cruciate starts from anterior side of tibia, while the posterior cruciate starts on the posterior side • Helpful hint: When you look at the back of the knee you see more of the posterior cruciate, when looking at front of the knee the anterior is most visible

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Joints and Articulations

The Knee: Menisci • Form the cushions between the articulating surfaces of the femur and the tibia • Made of fibrocartilage

The Knee: Menisci • The are “C” shaped with a thick rim and thinner center which helps to align the femur and tibia

Joint Pathologies

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Joints and Articulations

Arthritis • There are over 100 different types of arthritis • In general arthritis means inflammation of one or more joints • Involves the breakdown of the cartilage that protects bone • This inflammation can be caused by: • Wear and tear on the joint • Infection • Broken bone • Autoimmune disease • Common symptoms are inflammation, pain, stiffness and/or difficulty with movement, warmth around joint

Arthritis: Types • Osteoarthritis (OA) • The wear and tear arthritis • Causes: joints getting older, previous injuries, increased stress from obesity. In general any physical insults to the joint • Symptoms: joint pain and stiffness • Rheumatoid Arthritis (RA) • Affects around 1% of the population worldwide • It is a chronic, progressive autoimmune disorder. Joints are the most commonly affect sites of attacks, but it can affect other body parts. • Typically starts between ages 30-50, can affect younger and older people • Gout • Caused an attack of sudden burning pain, stiffness, and swelling in a joint, usually a big toe. • Gout is caused by too much uric acid in the blood, which may form crystals within the joints

Bursitis • Bursitis is inflammation of the fluid-fill sac, the bursa • -itis means inflammation • Can be acute or chronic • Can be caused by chronic overuse, trauma, RA, gout, infection, or it may also be idiopathic • Commonly occurs in shoulder, knee, elbow, and hip • Symptoms: • Tenderness when the joint is palpated • Stiffness and achiness when the join is moved • Swelling, warmth or redness at the join • Treatments can include NSAIDs, physical therapy, removing fluid from bursa, corticosteroid injection

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Joints and Articulations

Injury to the Joint Sprain • An injury to a join • Caused by the ligaments being stretched beyond their capacity • Symptoms include • • • •

Pain Swelling Bruising Decreased function

Strain • Injury to the muscle or tendon • The muscle fibers tear by overstretching • Symptoms include • • • •

Pain Local pain Stiffness Bruising

RICE • Depending on how server the sprain or strain, RICE may work just fine • Rest • Keep weight off the injury, let it rest • Ice • Ice reduces swelling, apply 10-15 minutes at a time • Compression • Wrap the join with bandages or ace-wraps. Be care NOT to cut off circulation • Elevation • Keep the injured area elevated, it helps reduce the swelling

Tendinitis • • • •

Inflammation, swelling of a tendon Can occur do to overuse, aging, injury Can also seen as part of a systemic disease like RA, diabetes Can occur anywhere there are tendons. Most commonly found • Elbow • Heel • Should • Wrist • Treatments can consists of rest, NSAIDs, steroid injections, etc.

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Joints and Articulations

Dislocation • Also known as a luxation • The joint becomes misaligned • Can vary in severity • A subluxation is a partial dislocation • Offending bone muse be reduced, set back in alignment

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